In general, this invention relates to capacitors; more particularly, it relates to a hermetically sealed film capacitor and a method for mass producing a hermetically sealed film capacitor.
Hermetically sealed film capacitors have widespread uses, particularly in electronic equipment that must meet stringent reliability requirements for operating in adverse environments. Because hermetically sealed capacitors have such widespread uses in electronic equipment, and often many such capacitors are needed in circuits within such electronic equipment, such capacitors are made on a high-volume basis. It is accordingly desirable to provide a method of mass producing hermetically sealed film capacitors with low material and manufacturing costs, consistent with the need for high reliability of the capacitors.
Various types of materials have been used to form a hermetically sealed case for a film capacitor. Very commonly, some type of metal has been used to make essentially all of the case, with various insulating materials such as glass being combined with the otherwise all-metal case so that electrically conductive terminal leads for the capacitor are insulated from the metal of the case.
Other materials that have been proposed for use in a sealing case are electrically insulating. U.S. Pat. No. 4,614,995 to Lavene is directed to a planar terminated surface mount capacitor having an electrically insulating casing element to which box-shaped metal end caps are bonded. Lavene teaches, in general way, using some type of ceramic as the material for the casing element. The material and manufacturing costs involved in making a capacitor such as Lavene proposes include the cost of providing an expensive noble metal (silver or gold), which is deposited to provide two ceramic-bonded metallization layers shaped in the form of outer-periphery bands surrounding the ceramic casing element. Less expensive hot tin is deposited over the noble metal bands. As to the labor or other manufacturing costs, these include costs attributable to the need to fit each end cap precisely so that all of four inwardly-facing surfaces of the end cap abut the outer-periphery band during a soldering operation to secure and seal the box-shaped end cap to the ceramic casing element.
A need exists for a low cost, reliable, hermetically sealed capacitor.